Abstract

Little is known about the constraints that neuromodulation places upon neural coding. We investigated the relationship between cholinergic modulation of spike timing and rate in a compartment model of a neocortical neuron. Our results suggest that cholinergic modulation of spike timing is directly related to the modulation of spike rate via the insertion of new spikes, and that spike timing is best preserved when the firing rate is low, i.e., when a rate code is ineffective (Thorpe et al., Nature 381 (6582) (1996) 520-522). We propose that neocortical neurons may use a spike timing and a rate code complementarily in different portions of their dynamic range.